Apparatus for making heat exchange tubes



Jan. 29, 1957 R. c. EDWARDS APPARATUS FOR MAKING HEAT EXCHANGE TUBESFiled Jan. 5, 1954 Fig. l I RAY, C. E DWA R D5 1 INVENTOR.

FIG.IO

United States Patent 2,779,222 APPARATUS FOR HEAT EXCHANGE Ray C.Edwards, Pompton Plains, N. J. Application January 5, 1954, Serial No.402,264 6 Claims. (Cl. 80-12) This invention relates to heat exchangetubes and more specifically to an apparatus for making a heat exchangetube particularly, though not exclusively, adapted for use inrefrigerant evaporators or analogous devices.

More specifically the invention relates to an apparatus for making heatexchange tubes which are provided with internal radiation fins whichradiate inwardly towards the axis of the tubes.

With these and other objects in view, as may appear from theaccompanying specification, the invention consists of various featuresof construction and combination of parts, which will be first describedin connection with the accompanying drawings, showing an apparatus formaking heat exchange tubes of a preferred form embodying the invention,and the features forming the invention will be specifically pointed outin the claims.

In the drawings:

Figure l is a fragmentary perspective view of the heat exchange tubeconstructed in accordance with the present invention.

Figure 2 is a fragmentary view partly in side elevation and partly inlongitudinal section showing a heat exchange tube of the presentinvention prior to the formation of the external fins thereon.

Figure 3 is a cross section taken on the line 3-3 of Figure 2, showingin dotted lines the means employed in forming the extruded radiationfins on the inner surface of the tube.

Figure 4 is a fragmentary plan view of the fin extruding device.

Figure 5 is a longitudinal section through the fin extruding device andtaken on the line 5-5 of Figure 4.

Figure 6 is a cross section taken on the line 6--6 of Figure 5.

Figure 7 is a composite view showing in section a set or series ofextruding rollers used in the forming of the extruded internal fins.

Figure 8 is a view partly in side elevation and partly in longitudinalsection showing part of the apparatus employed for extruding fins fromthe interior of the tube.

Figure 9 is an end view of the structure shown in Figure 8.

Figure 10 is a fragmentary plan view of a modified form of the tool ordevice used in extruding the internal fins.

Figure 11 is an end view of the tool or device shown in Figure 10 of thedrawings.

Referring more specifically to the drawings, Figure 1 shows aperspective of a fragment of a complete heat exchange tube forming thesubject matter of the present invention. This tube 1 is made of anyfully annealed metal such as copper, or the like normally used in theconstruction of heat exchange tubes used in evaporators, condensers oranalogous structures most generally employed in refrigerant apparatusalthough applicable for other uses. The tube 1 has a plurality ofradiation fins 2 upon its outer surface. The fins 2 are formed byspirally winding a laterally crimped metallic ribbon or strip about thetube, in .edgewise engagement therewith in the manner and as describedin either of my prior Patent Nos. 2,635,571 issued April 21, 1953, or2,661,525 issued December 8, 1953. If it is desirable and the use towhich the tube is to be put warrants it these external fins 2 may bewound flatwise upon the tube in the manner as shown in my applicationSerial No. 389,277 filed October 30, 1953. 'The tube 1 has a pluralityof circumferentially spaced inwardly projecting longitudinally extendingradiation fins 3 formed on its inner surface. These fins 3 extendlongitudinally of the tube substantially parallel with the longitudinalaxis of the tube so as to permit unimpeded flow of a coolant through thetube and the provision of these internal radiation fins 3 together withthe external radiation fins 2 permit of a maximum heat transferrelationship through the tube.

The present invention also embraces the method of making or extrudingthe fins 3 together with the apparatus for so doing. The apparatus forextruding the fins 3 is shown in Figures 4'to 9 inclusive with themodified form of part of the apparatus shown in Figures 10 and 11.

Figures 4, 5 and -6 of the drawings show an arbor or mandrel 5 which hasa plurality of longitudinally spaced diametrically extending openings 6milled or otherwise cut therein. Metal extruding rollers 7 are rotatablymounted in the openings 6 on suitable pins 8. The rollers '7 have theirperimeters grooved as clearly shown in Figures 4, 6 and 7 and they arearranged in sets with the grooves in the perimeters of all of therollers in each set being identically cut. The rollers in theprogressive sets are indicated as A, B and C in Figure '7 of thedrawings, and it will be noted that the grooves 10 in the roller 7a are.of the maximum width and depth with the greatest degree .of angularitybetween their sidewalls and these rollers 7a which form the first set ofrollers to engage the interior of the tube 1 are so shaped as toinitially extrude metal from the inner wall of the tube 1 to form theinternal fins .3. The grooves 11 of the rollers 7b and 7c in thesuccessive sets vof rollers carried by the arbor 5 are so shaped that asthey successively engage the metal extruded by the initial rollers 7athey extend and reduce the .cross sectional area of the extruded fins toform the fins 3 in their desired most practical set radiation shape andsize.

The rollers of each set are disposed so that the perimeter of one of therollers projects beyond the perimeter of the arbor 5 at one side of theaxis .of the arbor while the other roller protrudes .at a diametricallyopposed side of the arbor and thus when the arbor is forced through thetube 1 the fins are extruded at diametrically opposed portions of theinterior of the tube. The rollers have a maximum width corresponding toa predetermined portionof the surface of the interior .of the tube asclearly shown in Figures 3, 4 and 6 of the drawings. In fabrication oftubes .of the type constituting the present invention a tube of a heavywall preferably of a fully annealed material such as fully annealedcopper or the like is employed; for example, a 1" O. D. diameter tubewith a wall thickness of .050". The tube is encased wit in a metal block15 (shown in Figures 8 and 9 of the drawings) which metal block isformed of two sections having recesses 16 in their inner facing sideswhich correspond exactly to the outside diameter .of the tube to befinned and the block 15 wholly encase the tube and rigidly support it soas to prevent distortion of the tube during the extruding of theinternal fins thereon. The block 15 may be of such weight that it initself will rigidly support the tube in place or if it is desired one ofthe sections of the block 15 may .be rigidly supported and the othersection forced thereagainst and against a tube placed within therecesses in the block by pneumatic or hydraulic cylinder and pistonstructures 17 of any approved type which may be purchased upon the openmarket.

After the tube 1 is firmly and rigidly supported in the metal block 15the arbor 5 is drawn or forced through the interior of the tube. Theexterior diameter of the arbor which is a round rod is approximately.90" for a 1" O. D. tube and the rollers project beyond the outsidediameter of the arbor sutficiently so that their grooved perimeters willengage the interior of the tube for extrudportions of the interior ofthe tube, said sets of rollers arranged in groups with all of thecorresponding rollers in ing metal from its inner wall as the arbor isforced through the tube. As previously described, the perimeters of therollers 7 are grooved to form ridges 18 which may or may not be outabout a radius so that their periphery falls on the circumference of thewheel. The ridges of the rollers maintain a constant depth but the sidesof the ridges of the successive rollers are progressively steeperresulting in a final roller in which the width of the groove cut in theroller would be approximately .050" and a depth corresponding to theheight of the fin to be extruded. The complete internal finning of atube requires successive passing of the tool or arbor through the tubeat successively radially displaced positions until the fullcircumference of the interior of the tube is finned. The rolls may be solaid out and of such width that approximately 3, 4 or 5 passes of thearbor through the tube would be sufiicient to completely fin theinternal surface of the tube.

However, the present invention also embraces the pro vision of the metalextruding fin forming tool or arbor which will completely fin theinterior of the tube in one pass therethrough and such a tool is shownin Figures and 11 of the drawings. In the form of arbor shown in Figures10 and 11 of the drawings a group of the initial extruding rollers 7acomprising a plurality of sets, for instance six sets, is provided withthe rollers in each set spaced similarly to the rollers in the setsshown in Figure 5, i. e., with the perimeter of one roller of each setextending beyond the diameter of the arbor 5' at a point diametricallyopposite that from which the perimeter of the other roller 7a proiects.In the grouping of the sets of rollers as shown in Fi ure 10 the rollersin the adiacent sets are disposed with their axes at an acute angle tothe axes of the rollers in the adjacent set so that sufiicient sets ofrollers are provided in each group and are so located that they willextrude metal from the entire circumference of the interior of the tubeand thus with an arbor formed as shown in Figures 10 and 11 carrvin aplurality of groups of the successive rollers 7a, 7b and 70 a tube canbe internally finned with one pass of the arb r or tool through thetube.

While Figure 7 shows three thin extruding and shaping rollers. it is tobe understood of course that this number may be varied as required toproperly extrude and sha e the fins and there may be 3. 4, 5 or anyrequired number of rollers em loyed. e ch distinctive type arranged insets as hereinabove described.

It will be underst od that the invention is not to be limited to thespecific construction or arran ement of parts shown. but that thev mavbe Widely modified within the invention defined by the claims.

What is claimed is:

1. Means for forming radiating fins on the inner sur face of a heatexchange tube comprising an arbor, a plurality of metal extrudingrollers carried by said arbor and having their perimeters grooved toextrude metal from the inner surface of the tube and form extruded metalinto fin shape, said rollers arranged in sets having correspondinggrooved perimeters with the adjacent rollers of each set arranged toengage diametrically opposed portions of the interior of the tube.

2. Means for forming radiating fins on the inner surface of a heatexchange tube comprising an arbor, a plurality of metal extrudingrollers carried by said arbor and having their perimeters grooved toextrude metal from the inner surface of the tube and form extruded metalinto fin shape, said rollers arranged in sets having correspondinggrooved perimeters with the adjacent rollers ofeach set arranged toengage diametrically opposed each successive set in each group havingparallel axes. 3. Means for forming radiating fins on the inner surfaceof a heat exchange tube comprising an arbor, a plurality of metalextruding rollers carried by said arbor and having their perimetersgrooved to extrude metal from the inner surface of the tube and formextruded metal into fin shape, said rollers arranged in sets havingcorresponding grooved perimeters with the adjacent rollers of each setarranged to engage diametrically opposed portions of the interior of thetube, the extruding rollers of the sets which successively engage thetube having their perimeter shaped to engage and further form the metalextruded by the rollers of the set which initially engages the tube.

4. Means for forming radiating fins on the inner surface of a heatexchange tube comprising an arbor, a plurality of metal extrudingrollers carried by said arbor and having their perimeters grooved toextrude metal from the inner surface of the tube and form extruded metalinto fin shape, said rollers arranged in sets having correspondinggrooved perimeters with the adjacent rollers of each set arranged toengage diametrically opposed portions of the interior of the tube, theextruding rollers of the sets which successively engage the tube havingtheir perimeter shaped to engage and further form the metal extruded bythe rollers of the set which initially engages the tube, said sets ofrollers arranged in groups with the axes of the rollers of thecorresponding rollers in each group disposed at acute angles to the axesof the rollers of all other groups so as to engage and extrude metalfrom the entire internal surface of the tube in one pass of the arborthrough the tubes.

5. Means for forming radiating fins on the inner surface of a heatexchange tube comprising an arbor, said arbor provided with a pluralityof longitudinally spaced diametrically extending openings therein, metalextruding rollers rotatably mounted one in each of said openings, saidrollers arranged in sets and having their perimeters grooved to extrudemetal from the inner surface of a tube each in successive degrees ofextrusion whereby the rollers in each set will form completed internalfins in a tube when drawn longitudinally through a tube, the rollers inone set projecting beyond the perimeter of the arbor diametricallyopposite of the rollers in the other set whereby during the finextruding action each set of rollers will form back up support for thediametrically opposed set of rollers to prevent distortion of the tube.

6. Means for forming radiating fins on the inner surface of a heatexchange tube as claimed in claim 5, wherein said sets of rollers arearranged in groups with the axes of the corresponding rollers of eachgroup disposed at acute angles to the axes of rollers of all othergroups so as to engage and extrude metal from the entire internalsurface of the tube and form completed fins in the tube in one pass ofthe arbor through the tube.

References Cited in the file of this patent UNITED STATES PATENTS1,472,719 Harvath Oct. 30, 1923 1,584,772 Hyde May 18, 1926 1,816,159Smith July 28, 1931 1,865,575 Locke July 5, 1932 1,881,610 'Hyde Oct.11, 1932 2,238,798 Lenk Apr. 15, 1941 2,467,668 Hallberg Apr. 19, 19492,508,518 Hill May 23, 1950 2,598,191 Penn May 27, 1952 2,627,652SchWeller Feb. 10, 1953 FOREIGN PATENTS 16,340 Great Britain of 1899111,528 Australia Sept. 26, 1940

